Propuesta de modelo de trauma vascular mediante la caracterización mecánica de prótesis endovasculares (stents) a través del análisis estructural con técnicas FEA / Proposed model of vascular trauma by mean of mechanical characterization of endovascular prostheses (stents) based on structural analysis by FEA

Resumen Objetivo Tras las evidencias acumuladas mediante el uso de técnicas de angioplastia con stents, surge la polémica sobre los factores que inciden en la respuesta final, ya que hay estudios que reportan reestenosis de la luz en el 30-40% alrededor de 6 meses luego de ser implantados, vinculándose como una de las causas al diseño del dispositivo. Este artículo propone la caracterización funcional de stents endovasculares, analizando su influencia mecánica en el sistema vascular y prediciendo los factores de trauma implícitos en el lecho de los vasos. Métodos Utilizando modelos computacionales de prótesis endovasculares tipo stents, mediante técnicas Finite Elements Analysis, se procedió al análisis estructural de dichos dispositivos con el fin de predecir el comportamiento mecánico y el trauma vascular. Para ello, las prótesis fueron consideradas estructuras tubulares compuestas por múltiples eslabones que están sometidos a cargas de presión, que se reflejan como concentradores de esfuerzos. Resultados El estudio permitió visualizar cómo se ajusta la geometría del stent a las diferentes cargas, obteniéndose una aproximación a la respuesta de interacción "sólido-sólido" entre el stent y la pared arterial. Así, se caracterizó el patrón de esfuerzos y se planteó un modelo conceptual que explica su incidencia mecánica en la interacción stent-vaso, para inferir en la funcionalidad del diseño del dispositivo. Conclusiones El modelo conceptual planteado permite determinar la relación entre las condiciones de interacción mecánicas del stent, y advierte sobre los efectos en lo que sería la operación del dispositivo en el ambiente vascular.

Abstract Objective The accumulated evidence on angioplasty techniques with stents has raised a controversy about the factors that influence the final vascular response. Indeed, several studies have shown there might be re-stenosis between 30% to 40% about 6 months after placement, relating to the design of the device as one of the main causes. This paper proposes the functional characterization of endovascular stents, analyzing its mechanical influence in the vascular system and predicting implicit traumatic factors in the vessel. Methods A structural analysis was made for several computational models of endovascular stents using Finite Element Analysis in order to predict the mechanical behavior and the vascular trauma. In this way, the stents were considered as tubular devices composed of multiple links under radial pressure loads, reflecting stress concentration effects. Results The analysis allowed to visualize how the geometry of stents is adjusted under several load conditions, in order to obtain the response of "solid-solid" interaction between the stent and the arterial wall. Thus, an analysis was performed in order to calculate stress, and a conceptual model that explains its mechanical impact on the stent-vessel interaction, was raised, to infer on the functionality from the design of the devices. Conclusions The proposed conceptual model allows to determine the relationship between the conditions of mechanical interaction of the stents, and warns about the effects in what would be the operation of the device on the vascular environment.

Modelos e análises computacionais em neurociências: revisão sistemática / Computational models and analyses in neuroscience: systematic review

Os modelos computacionais do cérebro humano podem ser classificados em ‘modelos para tratamento de dados’ (i.e. mapas de coordenadas cerebrais) e ‘modelos de princípios operacionais’ (modelos conexionistas). A literatura relativa a ambos é vasta e muito variada, o que dificulta a realização de revisões sistemáticas. O objetivo do presente artigo é contribuir para o suprimento desta demanda e fornecer uma visão dos desenvolvimentos mais interessantes em andamento. Método: além dos métodos tradicionais de revisão, foi utilizado um programa para reconhecimento e quantificação de padrões em sistemas complexos (i.e. genomas). Resultados: entre os 2749 estudos do campo, aprendizado e memória são os tópicos mais recorrente, modelados em 0.14 e 0.9 dos estudos; Epilepsia, esquizofrenia e Parkinson são as doenças mais modeladas computacionalmente; Alzheimer é a quarta, sendo por sua vez mais relacionada à MRI (r=0.5435) do que à MEG (r=0.2033), PET (r=0.4718) e EEG (r=0.1766). Entre os 87 estudos 2007-2009 em ‘modelos de princípios operacionais’, o conceito mais proeminente é o de arquiteturas de pequenos mundos. O projeto mais excitante em desenvolvimento é o Blue Brain Project, que objetiva a criação de um modelo computacional do cérebro todo

Computational models of the human brain may be classified as ‘data treatment models’ (brain maps) and ‘operational-inspired models’ (connectionist models). The literature on both is extensive and varied, rendering difficulties to systematic reviews. This paper aims to contribute to outfit such demand, and to provide an overview of the most exciting projects currently under development. Method: besides traditional revising methods, a data mining program used to acknowledge patterns in complex databases (e.g. genomes) was used. Results: among the 2749 studies, learning and memory were the most recurrent topics, modeled in 0.14 and 0.9 of the studies. Epilepsy, schizophrenia and Parkinson are the most computationally simulated diseases; Alzheimer is the fourth, and more correlated to MRI (r=0.5435) than to MEG 9r=0.2033), PET (r=0.4718) and EEG (r=0.1766). Among the 87 2007-2009 studies on ‘operational-inspired models’, small world architectures is the most prominent concept. The most exciting project under development is the Blue Brain Project, which aims to provide a computational model of the whole brain